1. Field of the Invention
The present invention relates to gating structure for molds and, particularly, to a gating structure for controlling injection mold of plastic parts.
2. Discussion of the Related Art
Some products made of a polymer or other plastic are typically created by injection molding. During a typical injection molding process, a molten material is injected into a mold cavity via a runner. The molten material filled in the cavity is cooled and is set or solidified to form the molded product. However, if the molten material is directly injected into the mold cavity, the molten material will be effected by a resistance from the mold cavity such that defects such as flow marks will appear in the final product. It is necessary to adopt different gating designs for different molded product structures so as to eliminate defects. The gating structure is generally a structure that connects the runner and the mold cavity. After injection molding, scraps or swarf are formed at the gating structure. These scraps are usually referred to as ‘gate’. In conventional technology, gates of many different types such as edge gate, tab gate, fan gate, submarine gate, and pin gate are used. Different gates are suitable in different places and using an improper gating structure will cause high injection pressure, long cycle time and non-uniform shrinkage.
One kind of typical gating structure for molding is represented in FIG. 4. The gating structure for molding includes a submarine gate 10 and a cylindrical gate 20. One end of the cylindrical gate 20 connects with a mold cavity 30, the other end of the cylindrical gate 20 connects with an ejector pin 40. In order to avoid forming defects through non-uniform shrinkage, the diameter of the cylindrical gate 20 is the same as a width of the mold cavity 30. Accordingly, the diameter of the cylindrical gate 20 is limited. Furthermore, the molten material flow is slowed so that the finished result is effected. Especially for thin molded products, the effect will be more obvious.
Therefore, an improved gating structure is desired in order to overcome the above-described problems.